Summary A Helio H-295 Super Courier, C-FOMI, with only the pilot on board, took off from Smithers, British Columbia, with full fuel tanks. The pilot landed at FortSt.James to pick up a passenger and took off for Calgary (Springbank), Alberta. A logger working in the Hugh Allan Creek area heard the aircraft passing overhead. He heard two loud cracks and looked up to see that the right wing had separated from the aircraft, which was spiralling downward, trailing debris. The aircraft crashed at approximately 1600 Pacific daylight time, 37nautical miles southeast of Valemount. No fire occurred. Both occupants were fatally injured. Ce rapport est galement disponible en franais. Other Factual Information Before the flight, the pilot received a full weather briefing from the Smithers Flight Service Station (FSS) at about 1115Pacific daylight time (PDT).1 Weather conditions were reported suitable for flight along the route in accordance with visual flight rules. Actual weather at 1600 at the Blue River airport, 36nautical miles southwest of the accident site, was as follows: wind 190 true at 2knots; visibility more than 15statute miles; a few clouds at 300feet and 2500feet; broken clouds at 4500feet, 12000feet, and 30000feet; temperature 13.6C; and dew point 10.5C. A report was received from a pilot who took off from Valemount at 1443 (about 1 hours before the accident), intending to fly in the general area of the accident. He observed a large thunderstorm cell over the north end of McNaughton Lake and decided to return to Prince George. En route between Valemount and Prince George, visual meteorological conditions prevailed, numerous thunderstorm cells were present, and there were areas of light to moderate turbulence along certain areas of the Fraser River. Visual and infrared satellite photographs for 2300 Coordinated Universal Time (1600 PDT) were examined but did not reveal any obvious thunderstorm activity. A lightning detection program was run but did not detect any strikes in that region for 24hours before and after the time of the accident. Wreckage was found in a steep, wooded area adjacent to a logging road at approximately 4500feet above sea level. This site is 4630m southeast of a 9080-footpeak in the Selwyn Range. Damage to trees near the wreckage indicates that the aircraft struck the ground in a vertical descent, consistent with the observation that it was spiralling out of control with one wing detached. Fuel was found in the left wing tanks. Fuel cell debris from the right wing was found by the side of a logging road, 175 m from the main wreckage. The right wing was found 575m from the main wreckage, and the right aileron was found lodged in a tree above. The left aileron, trailing edge flaps, and leading edge slats were ripped off the wing structure and were not found. The wreckage was recovered from the accident site for a more detailed examination at the TSB regional wreckage examination facility. Damage and contact markings indicated that the slats had deployed violently before being ripped off the wings. The flaps were torn away at their attachments while in the up position. Fretting corrosion marks were found on both lower wing attachment points. The right wing main spar was found to have failed in overload about one foot outboard of the carry-through structure. The wing structure showed torsional deformations consistent with failure occurring in an upward and aft direction. The pilot held a valid private pilot licence. He had accumulated a total of 3585hours of flying time as of 28February2001 and had been flying this particular aircraft since 1990. Logbooks and maintenance records indicate that the aircraft had been certified, equipped, and maintained in accordance with existing regulations and approved procedures. The aircraft had no known deficiencies before the flight. The airframe had operated 2651.2hours as of 09July2001. The engine had operated 994.2hours since overhaul. The last recorded maintenance was to overhaul the propellor on 30November2000. The last annual inspection was accomplished on 11August2000. The aircraft was due for a 100hour inspection or annual inspection, whichever came first, no later than 11August2001, nine days before the accident. The aircraft was loaded with a considerable amount of gear, consisting of survival equipment, audiovisual equipment, and personal effects. When the wreckage was recovered, these articles weighed 340 pounds. The aircraft was operated close to its maximum allowable weight and was within its centre-of-gravity limits. At the time of the accident, the aircraft was airborne for about 2hours25 minutes, consumed about 130L (approximately 220pounds) of fuel, and weighed approximately 3600pounds, 200pounds below its maximum gross weight. This Helio Courier H-295, serial number 1475, operated under a supplemental type certificate (STC), number SA1589CE, in the normal category. The STC was issued as part of a type design change to increase the maximum allowable gross weight from 3400 to 3800pounds. The STC was issued 30May1980, amended 05 February 1981, and re-issued 31May1983. This STC did not require an inspection of the wing spar to carry-through structure for cracks or corrosion. A search of the TSB database revealed two similar occurrences of in-flight wing structural failure (reports A93P0013 and A78P0084) and another instance of structural damage caused by severe turbulence (report A94W0174) to Helio Courier H-295 aircraft in Canada. A search of the US National Transportation Safety Board (NTSB) database revealed one occurrence of in-flight wing structural failure to a Helio Courier H-295 aircraft in the US since 1983. The aircraft was originally certificated by the Federal Aviation Administration (FAA) in the normal category, which calls for the aircraft to be designed to withstand a limit load factor of +3.8g and -1.52g and an ultimate load factor of +5.7g and -2.28g. In other words, a loading on the aircraft structure - either by pilot input through the flight controls or environmentally by means of a gust - of up to +3.8g would not cause permanent deformation or structural damage to the aircraft. Some structural damage could be expected if the limit load factor exceeds +3.8g, depending on the extent to which this limit is exceeded. Failure of a primary structural component would be expected if the ultimate load factor exceeds +5.7g. If the limit load factor was previously exceeded, the ultimate load factor would be compromised. Limit load is a product of limit load factor and gross weight and is constant for all weights above design gross weight. Since the limit load is constant, if the gross weight is increased (example, 3400 to 3800pounds), the limit load factor is reduced, in this case from 3.8g, to 3.4g. A warning in the Airplane Flight Manual carried in the aircraft states: Use controls with caution above 125 mph (109 [knots]) CAS [calibrated airspeed]. In gusty air, it is advisable to reduce cruising speed below normal, and in severe turbulence reduce speed below 94 mph (flaps up) and below 65 mph (flaps down). Use controls with caution above 125 mph (109 [knots]) CAS [calibrated airspeed]. In gusty air, it is advisable to reduce cruising speed below normal, and in severe turbulence reduce speed below 94 mph (flaps up) and below 65 mph (flaps down). Airspeed indicators in the aircraft are marked with colour-coded radials and arcs to facilitate pilot recognition of important airspeeds: A radial red line marks the never-exceed speed, which is the maximum safe airspeed. A yellow arc on the outside of the instrument denotes a range of speeds in which operations should be conducted with caution and only in smooth air. A green arc denotes the normal operating speed range. A white arc denotes the speed range in which flaps may be safely lowered. When this aircraft's gross weight was increased under the STC, several of the limiting airspeeds (in mph CAS) were changed to reflect the new maximum weight: The never-exceed speed (red radial) was reduced from 200 to 167. The caution range (yellow arc) was reduced from 160-200 to 133-167. The design cruising speed was reduced from 160 to 133. The normal operating range (green arc) was changed from 60-160 to 60-133. The maximum design manoeuvring speed was increased from 103 to 107. The airspeed indicator was not changed, nor were any modifications made to reflect these changes in limiting airspeeds and airspeed ranges. The STC had no requirement to change or modify the airspeed indicator. The airspeed indicator incorporated a dual layout, presenting airspeed information in knots on the outside of the dial and in mph on a smaller scale on the inside of the dial. A comparison between the right aileron and its factory drawing shows a number of discrepancies. These discrepancies were apparently perpetuated in field maintenance because, until recently, the factory drawing was proprietary and unavailable. Maintenance reference information on aileron balance and aileron free play is also not readily available.